Muhammad Firdaus Omar

Photocatalytic degradation of paraquat dichloride over CeO2-modified TiO2 nanotubes and the optimization of parameters by response surface methodology

Decontamination of water sources by one-dimensional (1D) nanostructured TiO2 holds great potential due to their unique electronic and textural properties. In this study, CeO2-modified TiO2 nanotubes (Ce–TNTs) have been prepared by impregnation of CeO2 on hydrothermally synthesized TiO2 nanotubes (TNTs). The catalysts were characterized by XRD, HRTEM, EDX, STEM, EELS, DR-UV/VIS spectroscopy and nitrogen adsorption (NA) analyses. The photocatalytic activities of the synthesized Ce–TNTs were examined on the degradation of paraquat dichloride (PQ) under UV light. The modification of TNTs with CeO2 led to an enhancement of the photocatalytic activity. Box–Behnken design (BBD) based on response surface methodology (RSM) was used to optimize three experimental parameters namely; CeO2 ratio, calcination temperature and catalyst loading. ANOVA of the generated quadratic model yielded a coefficient of determination, R2 of 0.9926 and probability, P < 0.0001, which confirms that the model is suitable for predicting the optimum degradation efficiency of PQ. Based on this model, the calcination temperature and CeO2 ratio were the most significant parameters and the interactions between these parameters and the catalyst loading were also significant. The predicted optimum conditions that would give a maximum of 80.798% degradation of PQ in 4 h were 9.01% CeO2 ratio, 760.49 °C calcination temperature and 0.38 g catalyst loading. Validation experiments were conducted in triplicate and an average of 80.27% degradation of PQ was achieved which is in agreement with 80.798% predicted. Under these optimum conditions, TOC analysis showed that 51.10% mineralization of PQ was achieved within 4 h. Therefore, this work further confirms that the photocatalytic treatment of organics-contaminated water can be designed and optimized by RSM.

Electron Microscopy Studies on the Growth of Well-Aligned NiSi/SiC Core-Shell Nanowires Synthesized by HWCVD

Well-aligned NiSi/SiC core-shell nanowires were grown on Ni-coated p-type crystal Si (100) substrates by using hot-wires chemical vapor deposition (HWCVD) technique. The growth of the nanowires was performed at a substrate temperature of 450°C and facilitated by a hot-filament at a temperature above 1800°C. Electron microscopy characterizations were employed to investigate the morphology, and microstructure properties of the nanowires. A high-resolution transmission electron microscopy (TEM) images indicate that the nanowires were structured by single crystalline NiSi and amorphous SiC as the core and shell respectively. Moreover, the TEM images showed presence of 3C-SiC nano-crystallites embedded within an amorphous matrix in the shell.

Luminescent Properties of SiC Thin Film Deposited by VHF-PECVD: Effect of Methane Flow Rate

Bulk silicon carbide (SiC) as light emitter is less efficient due to its indirect bandgap. Therefore, nanosized SiC thin film fabrication approach enable emission wavelength shifts due to spatial confinement. The result of luminescent study of SiC thin film deposited via very high frequency plasma-enhanced chemical vapour deposition (VHF-PECVD) are presented. Precursor gasses used were silane and methane. Methane flow rate was varied from 8 sccm to 20 sccm while other parameters were maintained. Raman spectral analysis denotes the quantum confinement effect occurrence in proportion to the methane flow rate increment. The luminescence properties of the deposited SiC thin film ranging from highly green emission (~518 nm) to highly UVB emission (~294 nm) dominant luminescence. Broad blue emission band shifted toward higher wavelength with smaller FWHM as methane flow rate is increased. This results enable the possibility of luminescent SiC thin film applications in photonics and electronic integration as blue light sources.

Substrate temperature dependent surface morphology of nanostructured zinc antimonides thin films

The growth and characterization of nanostructured zinc antimonides thin films are reported in this work. The nanostructured zinc antimonides thin films were prepared by RF magnetron sputtering using a single sputtering target. The range of growth parameters was determined for substrate temperature (50°C-150°C), deposition time (600 s), argon flow rate (5 sccm) and RF power (50 W). The effects of manipulated growth parameters on surface morphology were investigated. XRD, EDX, FESEM and AFM were utilized to characterize the deposited thin films. Based on XRD characterization, Zn and Sb peaks are not captured in XRD patterns. The very low intensity of reflected peaks along 2Θ shows that the formation of deposited thin films is in amorphous form. From EDX characterization, it is confirmed that Zn and Sb elements existed in each deposited thin films. Zn seems to have relatively higher composition than Sb in each deposited thin films. It can be concluded that the growth parameters contributed to the deviation of the elementary composition. The AFM characterization shows the formation of nanograins and nanodots are depending on manipulated substrate temperature. As substrate temperature increased, it is found that the nanograins diameter is increased, low grain density and decreased in average roughness. It is confirmed that the height distribution of the nanograins and nanodots cause the surface to become rougher.